Dynamic energy-efficient transmit point (TP) muting for virtual radio access network (V-RAN)

ABSTRACT

Operational and environmental efficiency in virtual radio access networks (VRANs) can be improved by offloading data traffic and/or control signaling between physical transmit points (TPs) of a virtual TP. This may allow one or more physical TPs of the virtual TP to be muted in the downlink or uplink direction, thereby reducing energy consumption. The offloading may be performed during relatively short time-intervals such that physical TP are muted for one or more transmission time intervals (TTIs) before being re-activated. The offloading may also be implemented over longer time-intervals in accordance with a traffic engineering (TE) policy. Further it is possible to re-activate a de-activated downlink transmitter of physical TP by monitoring wireless signals via an activated receiver of the physical TP.

This patent application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 15/808,737 filed on Nov. 9, 2017 and entitled“Dynamic Energy-Efficient Transmit Point (TP) Muting for Virtual RadioAccess Network (V-RAN),” which is a continuation of U.S. Non-Provisionalpatent application Ser. No. 14/672,423, filed on Mar. 30, 2015 andentitled “Dynamic Energy-Efficient Transmit Point (TP) Muting forVirtual Radio Access Network (V-RAN),” now U.S. Pat. No. 9,877,259,which claims priority to U.S. Provisional Application No. 61/972,839,filed on Mar. 31, 2014 and entitled “Dynamic Energy-Efficient TransmitPoint (TP) Muting for Virtual Radio Access Network (V-RAN),” all ofwhich are incorporated by reference herein as if reproduced in theirentireties.

TECHNICAL FIELD

The present invention relates to green wireless communications, and, inparticular embodiments, to techniques for dynamic energy-efficienttransmit point muting for virtual radio access network (V-RAN).

BACKGROUND

Mobile network operators may often incur high operational expenses dueto the power requirements of base stations. For example, base stationsmay typically consume as much as eighty percent of the energy requiredto operate a cellular network, and may constitute a significant portionof the cellular network's carbon footprint. One strategy for improvingefficiency is referred to as transmit point (TP) muting, where basestations that are not serving UEs can be transitioned from an activemode to ‘sleep’ (dormant) mode. Techniques for implementing TP muting inwireless networks having high access point (AP) densities are desired.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved, by embodiments of thisdisclosure which describe techniques for dynamic energy-efficienttransmit point muting for virtual radio access network (V-RAN).

In accordance with an embodiment, a method for offloading trafficbetween physical transmit points (TPs) of a virtual TP in a wirelesscommunications network is provided. In this example, the methodcomprises identifying a virtual TP serving a user equipment (UE). Thevirtual TP includes at least a first physical TP and a second physicalTP. The first physical TP communicates one or both of data traffic andcontrol signaling with the UE during a first period. The method furtherincludes offloading at least one of the data traffic and the controlsignaling from the first physical TP to the second physical TP. Thesecond physical TP communicates the at least one of the data traffic orthe control signaling with the UE during a second period. An apparatusfor performing this method is also provided.

In accordance with another embodiment, a method for muting physical TPsis provided. In this example, the method includes deactivating adownlink transmitter of a physical transmit point (TP) withoutdeactivating the uplink receiver of the physical TP, monitoring uplinkfeedback signals via the uplink receiver while the downlink transmitterof the physical TP is deactivated, and reactivating the downlinktransmitter of the physical TP when the uplink feedback signal satisfiesa downlink re-activation criteria.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates a diagram of an embodiment wireless communicationsnetwork;

FIGS. 2A-2D illustrate diagrams of an embodiment virtual radio accessnetwork (VRAN) for offloading data traffic and/or control signaling;

FIG. 3 illustrates a diagram of an embodiment method for offloading datatraffic between physical access points (APs) of a virtual AP;

FIG. 4 illustrates a diagram of an embodiment method for offloadingcontrol signaling between physical access points (APs) of a virtual AP;

FIG. 5 illustrates a diagram of an embodiment method for re-activating adownlink transmitter based on uplink feedback information;

FIG. 6 illustrates a diagram of an embodiment Multicast-broadcastsingle-frequency network (MBSFN) frame structure;

FIG. 7 illustrates a diagram of a conventional Beyond Cellular GreenGeneration (BCG2) network architecture;

FIG. 8 illustrates a diagram of a conventional phantom cell networkarchitecture;

FIGS. 9A-9C illustrate network configurations for transmit point mutingand DPS scheduling that leverage device-to-device (D2D) communications;

FIG. 10 illustrates a diagram, graph, and chart of a load dependentpower consumption model;

FIG. 11 illustrates a diagram of a power consumption model;

FIG. 12 illustrates a graph of a system capacity analysis;

FIG. 13 graphs of a power consumption model;

FIGS. 14A-14C illustrate graphs of throughput simulations for embodimentpower reduction techniques;

FIG. 15 illustrates a chart of simulation scenario results;

FIG. 16 illustrates a diagram of an embodiment computing platform; and

FIG. 17 illustrates a diagram of an embodiment communications device.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

Base stations may consume as much as eighty percent of the energyrequired to operate a cellular network. For example, a power amplifierin macro base stations may be responsible for between approximatelyfifty-five and sixty percent of the macro base station's powerconsumption, while the power amplifier in low power nodes may beresponsible for approximately thirty percent of their power consumption.Accordingly, it may be possible to substantially reduce powerconsumption by dynamically deactivating a base station's downlinktransmitter when the base station is idle in the downlink. Likewise,power consumption may also be reduced by deactivating an uplink receiverof a base station when the base station is idle in the uplink. Sincepower consumption increases operating costs and environmental emissions,traffic engineering techniques for efficiently muting base stations aredesired.

Aspects of this disclosure improve operation and environmentalefficiency in virtual radio access networks (VRANs) by offloading datatraffic and/or control signaling between physical transmit points (TPs)of a virtual TP. This may allow one or more physical TPs of the virtualTP to be muted in the downlink or uplink direction, thereby reducingenergy consumption. In particular, offloading traffic/signaling from afirst physical TP to a second physical TP may allow the first physicalTP to be dynamically muted. Additionally, offloading traffic/signalingfrom a first physical TP to a second physical TP may be part of abroader plan/strategy to uplink and/or downlink mute a third physicalTP. The plan/strategy may be implemented dynamically such thatoffloading is performed during relatively short time-intervals, e.g.,physical TP is muted for one or more transmission time intervals (TTIs)before being re-activated, etc. The plan/strategy may also beimplemented over a longer term in accordance with a traffic engineering(TE) policy, e.g., physical TP is muted for several minutes or hours,etc. For instance, transferring traffic/signaling between low powernodes may be part of a broader TE strategy to offload control signalingfrom a macro base station. The offloading of data traffic and/or controlinformation may be transparent to the served UE, who may view a group ofphysical TPs as a single virtual TP. In some embodiments, differentphysical TPs of a virtual TP are assigned to communicate data trafficand control information. For example, one physical TP may be assigned tocommunicate downlink data traffic to the served UE, while anotherphysical TP may be assigned to communicate downlink control signaling tothe UE. Moreover, offloading of the control signaling may be performedindependently from the data traffic, and vice versa. For example, assumethat a first physical TP is communicating data traffic with a served UEduring a first period, and a second physical TP is communicating controlsignaling with the served UE during the first period. If the datatraffic is offloaded from the first physical TP to a third physical TP,then it may be possible to reduce power consumption at the firstphysical TP by downlink (or uplink) muting the first physical TP duringa second period. Likewise, if the control signaling is offloaded fromthe second physical TP to a third physical TP, then it may be possibleto reduce power consumption at the second physical TP through selectivemuting. Aspects of this disclosure also provide a wake-up technique forre-activating a downlink transmitter of a physical TP based on signalsmonitored by an uplink receiver of the physical TP. These and otheraspects are explained in greater detail below.

FIG. 1 illustrates a network 100 for communicating data. The network 100comprises an access point (AP) 110 having a coverage area 101, aplurality of mobile devices 120, and a backhaul network 130. The AP 110may comprise any component capable of providing wireless access by,inter alia, establishing uplink (dashed line) and/or downlink (dottedline) connections with the mobile devices 120, such as a base station,an enhanced base station (eNB), a femtocell, and other wirelesslyenabled devices. The mobile devices 120 may comprise any componentcapable of establishing a wireless connection with the AP 110, such as auser equipment (UE), a mobile station (STA), or other wirelessly enableddevices. The backhaul network 130 may be any component or collection ofcomponents that allow data to be exchanged between the AP 110 and aremote end (not shown). In some embodiments, the network 100 maycomprise various other wireless devices, such as relays, low powernodes, etc.

Aspects of this disclosure dynamically offload data traffic and/orcontrol signaling of a UE between physical TPs of a virtual TP to reducepower consumption and/or environmental emissions in the correspondingVRAN. FIGS. 2A-2D illustrate an embodiment network 200 for offloadingdata between physical TPs of a virtual TP. As shown, the embodimentnetwork 200 includes a virtual TP 210 composed of a plurality ofphysical TP 212, 214, 216, and a controller 230. The physical TPs 212,214, 216 are adapted to provide wireless access in a coverage area 201of the virtual TP 210. The controller 230 may be any componentconfigured to make scheduling and/or offloading decisions for thevirtual TP 210. The controller 230 may be co-located with one of thephysical TPs 212, 214, 216. Alternatively, the controller 230 may be acentral controller that is separate and distinct from the physical TPs212, 214, 216.

As illustrated in FIG. 2A, the physical TP 212 is communicating datatraffic (solid line) with a UE 220 during an initial period, and thephysical TP 214 is communicating control signaling (dashed line) withthe served UE 220 during the initial period. The data traffic andcontrol signaling may be communicated in the downlink direction and/orthe uplink direction. In one example, both the data traffic and thecontrol signaling are communicated in the downlink direction. In anotherexample, both the data traffic and the control signaling arecommunicated in the uplink direction. In other examples, the datatraffic is communicated in the downlink direction and the controlsignaling is communicated in the uplink direction, or vice versa.

The data traffic and/or the control signaling may be exchanged betweenphysical TPs of the virtual TP 210. In an example depicted in FIG. 2B,the data traffic is offloaded from the physical TP 212 to the physicalTP 216 between the initial period and a subsequent period. In such anexample, the physical TP 216 communicates the data traffic with theserved UE 220 during the subsequent period, and the physical TP 214communicates control signaling with the served UE 220 during thesubsequent period. The data traffic offloaded from the physical TP 212may be downlink data traffic or uplink data traffic.

When the offloaded data traffic is downlink data traffic, the physicalTP 212 may be downlink muted during the subsequent period if thephysical TP 212 does not have additional downlink transmissionresponsibilities during the subsequent period. Downlink muting mayinclude deactivating downlink baseband circuitry of a downlinktransmitter in the physical TP 212, deactivating a downlink radiofrequency (RF) chain of the physical TP 212, or both. The downlinkbaseband circuitry may include any components for performing processingtasks on a baseband signal prior to up-converting the baseband signal toan RF signal. The downlink RF chain may include any components forup-converting the baseband signal to an RF signal (e.g., up-converter,etc.), as well as any components for amplifying or otherwise processingthe RF signal prior to downlink transmission (e.g., power-amplifier,beamforming circuitry, etc.).

When the offloaded data traffic is uplink data traffic, then thephysical TP 212 may be uplink muted during the subsequent period if thephysical TP 212 does not have additional uplink receptionresponsibilities during the subsequent period. Uplink muting may includedeactivating uplink baseband circuitry of a downlink transmitter in thephysical TP 212, deactivating an uplink RF chain of the physical TP 212,or both. The uplink RF chain may include any components for receivingand/or processing an uplink RF signal (e.g., low noise amplifier, etc.),as well as any components for down-converting the RF signal to abaseband signal (e.g., down converter, etc.). The uplink basebandcircuitry may include any components for performing processing tasks ona baseband signal produced from down-converting the uplink RF signal.

In another example depicted in FIG. 2C, the control signaling isoffloaded from the physical TP 214 to the physical TP 216 between theinitial period and a subsequent period. In such an example, the physicalTP 212 communicates the data traffic with the served UE 220 during thesubsequent period, and the physical TP 216 communicates controlsignaling with the served UE 220 during the subsequent period.

The control signaling offloaded from the physical TP 214 may be downlinkcontrol signaling or uplink control signaling. In some embodiments, thecontrol signaling is user-specific control signaling. If the offloadedcontrol signaling is downlink control signaling, then the physical TP214 may be downlink muted during the subsequent period if the physicalTP 214 does not have additional downlink transmission responsibilities.Alternatively, if the offloaded control signaling is uplink controlsignaling, then the physical TP 214 may be uplink muted during thesubsequent period if the physical TP 214 does not have additional uplinkreception responsibilities.

In yet another embodiment depicted by FIG. 2D, both the data traffic andthe control signaling are offloaded to the physical TP 216 from thephysical TP 212 and the physical TP 214, respectively. One or both ofthe physical TP 212 and the physical TP 214 may be downlink and/oruplink muted during the subsequent period if they do not have additionaltransmission/reception responsibilities. It should be noted that theoffloading techniques depicted in FIGS. 2B-2D can be performed withoutcausing the UE 220 to undertake a handover.

It should be appreciated that the offloading examples demonstrated inFIGS. 2B-2D represent just some embodiments provided by this disclosure,and that other offloading strategies may be employed to, for example,reduce power consumption in a wireless network. In some embodiments, asingle physical TP (e.g., a first physical TP) may communicate datatraffic and control signaling to a UE during the initial period, and oneor both of the data traffic and control signaling can be offloaded toanother physical TP (e.g., a second physical TP) between the initialperiod and the subsequent period. For example, data traffic may beoffloaded from the first physical TP to the second physical TP withoutoffloading the control signaling. As a result, the first physical TP maycommunicate the control signaling to the UE during the subsequentinterval, while the second physical TP may communicate the data trafficto the UE during the subsequent interval. As another example, controlsignaling may be offloaded from the first physical TP to the secondphysical TP without offloading the data traffic. As a result, the firstphysical TP may communicate the data traffic to the UE during thesubsequent interval, while the second physical TP may communicate thecontrol signaling to the UE during the subsequent interval. As yetanother example, both the data traffic and the control signaling may beoffloaded from the first physical TP to the second physical TP. As aresult, the second physical TP may communicate both the data traffic andthe control signaling to the UE during the subsequent interval. As yetanother example, data traffic may be offloaded from the first physicalTP to the second physical TP, while control signaling may be offloadedfrom the first physical TP to a third physical TP. As a result, thesecond physical TP may communicate the data traffic to the UE during thesubsequent interval, while the third physical TP may communicate thecontrol signaling to the UE during the subsequent interval. Otherembodiments are also possible, e.g., data traffic could be offloadedfrom a first physical TP to a second physical TP, while controlsignaling is offloaded from a third physical TP to a fourth physical TP.

It should also be appreciated that offloading data traffic and/orcontrol signaling from a first physical TP to a second physical TP maybe part of a larger TE scheme to achieve downlink or uplink muting of athird physical TP. For example, data traffic and/or control signalingmay be offloaded from a first low power node to a second low power nodeso that the first low power node has the capacity to undertake offloadedtraffic/signaling from a macro base station. This may allow the macrobase station to be uplink or downlink muted during a subsequent period.

FIG. 3 illustrates an embodiment method 300 for offloading data trafficbetween physical TPs of a virtual TP, as might be performed by acontroller. As shown, the method begins at step 310, where thecontroller identifies a virtual TP.

Thereafter, the method 300 proceeds to step 320, where the controlleroffloads data traffic from a first physical TP of the serving virtual TPto a second physical TP of the serving virtual TP. Offloading the datatraffic may be accomplished by communicating instructions to one or bothof the physical transmit points. In some embodiments, the controllerconsiders muting the first physical TP after the data traffic has beenoffloaded. In such embodiments, the method 300 proceeds to step 330,wherein controller determines whether the first physical TP still hasuplink/downlink transmission/reception responsibilities. If not, themethod 300 proceeds to step 340, where the controller downlink or uplinkmutes the first physical AP. This may be performed by communicatinginstructions to the first physical AP. It should be noted, that uplinkdata traffic and/or downlink data traffic may be offloaded from onephysical AP to another. For example, a controller may identify aphysical AP having data traffic that can be offloaded, and then offloaduplink data traffic, downlink data traffic, or both from the identifiedphysical AP to another physical AP. In one embodiment, the controlleroffloads one of uplink (UL) data traffic and downlink (DL) data trafficfrom the identified physical TP to another TP without offloading theother one of the UL traffic and the DL traffic. In another embodiment,the controller offloads both uplink (UL) data traffic and downlink (DL)data traffic from the third physical TP to another TP.

In some embodiments, a controller may select a virtual TP for strategicoffloading between physical TPs of the virtual TP based on a policy orobjective. For instance, the controller may select, from a plurality ofvirtual TPs in a wireless network, one or more of the virtual TPs forstrategic offloading to achieve a specific objective, such as to reducethe overall power consumption or emissions of the wireless network. Inone example, the controller may select the virtual TP(s) in accordancewith a traffic level of the virtual TP(s). The traffic level maycorrespond to an amount of traffic being communicated by the physicalTPs of the virtual TP. For example, virtual TPs that have low trafficlevels and/or low amounts of available bandwidth may be better suitedfor strategic offloading, as the controller may have more flexibility tooffload traffic between physical TPs, thereby allowing the controller todynamically mute a higher number and/or ratio of physical TPs of thecorresponding virtual TPs. Hence, the controller may compare trafficlevels of virtual TPs when selecting a virtual TP for strategicoffloading. In another example, the controller may select the virtualTP(s) for strategic offloading in accordance with a power consumption ofthe virtual TP(s). For instance, the controller may be better able toreduce power consumption in a wireless network by selecting virtual TPshaving high power consumptions for strategic offloading, as virtual TPshaving high power consumptions may experience greater energy savingsfrom the strategic offloading.

FIG. 4 illustrates an embodiment method 400 for offloading controlsignaling between physical TPs of a virtual TP, as might be performed bya controller. As shown, the method begins at step 410, where thecontroller identifies a virtual TP. Thereafter, the method 400 proceedsto step 420, where the controller offloads control signaling from afirst physical TP of the serving virtual TP to a second physical TP ofthe serving virtual TP. Offloading the control signaling may beaccomplished by communicating instructions to one or both of thephysical transmit points. In some embodiments, the controller considersmuting the first physical TP after the control signaling has beenoffloaded. In such embodiments, the method 400 proceeds to step 430,wherein controller determines whether the first physical TP still hasuplink/downlink transmission/reception responsibilities. If not, themethod 400 proceeds to step 440, where the controller downlink or uplinkmutes the first physical AP. This may be performed by communicatinginstructions to the first physical AP.

Aspects of this disclosure also provide wake-up techniques fordynamically re-activating a downlink transmitter based on uplinkfeedback. More specifically, a physical TP that is downlink muted maymonitor signals via an activated uplink receiver, and re-activate thedownlink transmitter when a monitored signal satisfies a downlinkre-activation criteria. The monitored signals may include uplink signalsassociated with UEs or relay. For example, the signal may be an uplinksignal transmitted directly by a target UE. As another example, thesignal may be an uplink signal indicating a parameter or instructionassociated with a target UE. The uplink signal may be communicated bythe target UE, by a relay, or by a helping UE engaged indevice-to-device (D2D) communications with the target UE. In anembodiment, the uplink signal comprises an uplink feedback signal thatindicates an interference level experienced by a target UE. In such anembodiment, the downlink re-activation criteria may be satisfied whenthe uplink signal indicates that the interference level experienced bythe target UE exceeds a threshold. The interference level indicated bythe feedback signal may be a background interference level experiencedby the target UE. In another embodiment, the uplink signal comprises arequest or indication to provide wireless access to a target UE. Forexample, the uplink signal may comprise a discovery signal (e.g., anuplink sounding signal), and the downlink re-activation criteria may besatisfied when a quality (e.g., received signal power, etc.) of thediscovery signal exceeds a threshold. As yet another example, the uplinksignal may comprise a request for service (e.g., a handover or linkestablishment request). The monitored signals may also include signalscommunicated by other network devices, such as a wakeup signalcommunicated by a controller or another physical TP. The physical TP mayalso receive a wake-up indication from a controller or neighboring TPover a backhaul link.

Notably, a controller may know, or be able to estimate, how muchdownlink interference the UE will experience as a result of downlinktransmissions by physical TPs being managed by the controller.Background interference may include interference or noise observed atthe UE that exceeds the cumulative downlink interference from downlinktransmissions of physical TPs being managed by the controller. Theexcess interference may come from various sources, such as TPs not beingmanaged by the controller, other UEs, etc.

FIG. 5 illustrates an embodiment method for dynamically re-activating adownlink transmitter based on uplink feedback, as may be performed by aphysical TP. As shown, the method 500 begins with step 510, where thephysical TP deactivates a downlink transmitter of the physical TPwithout deactivating an uplink receiver of the physical TP. Thedeactivation may be a partial or full deactivation. For example, thephysical TP may deactivate a downlink baseband circuitry of the downlinktransmitter without deactivating a downlink radio frequency (RF) chainof the downlink transmitter. As another example, the physical TP maydeactivate the downlink RF chain of the downlink transmitter withoutdeactivating the downlink baseband circuitry of the of the downlinktransmitter. As yet another example, the physical TP may deactivate boththe downlink baseband circuitry and the downlink RF chain of thedownlink transmitter. Next, the method 500 proceeds to step 520, wherethe physical TP monitors signals using the uplink receiver while thedownlink transmitter is deactivated. The signals may be uplink signalstransmitted by a target or helping UE. Alternatively, the signals may bere-activation signals communicated by another TP. Subsequently, themethod 500 proceeds to step 530, where the physical TP reactivates thedownlink transmitter when a monitored signal satisfies a downlinkre-activation criteria.

Embodiments of this disclosure may provide greater flexibility thanconventional techniques, as well as providing increased independencybetween downlink and uplink operations. Combined data and controloffloading and techniques for efficiently transitioning transmit pointsfrom idle to active modes may provide flexibility, cost savings andperformance gains.

FIG. 6 illustrates a Multicast-broadcast single-frequency network(MBSFN) frame structure of conventional DTX schemes. As shown,transmissions are muted in a portion of (e.g., six of ten) MSBFNsubframes in a radio-frames to reduce base station power consumption.Details of the DTX scheme are discussed in the Vehicular TechnologyConference (VTC) article entitled “Reducing Energy Consumption in LTEwith Cell DTX,” (2011 IEEE 73rd, vol. 1, no. 5, pp. 15-18, May 2011),which is incorporated by reference herein as if reproduced in itsentirety.

FIG. 7 illustrates a Beyond Cellular Green Generation (BCG2) networkarchitecture in which the network is split into a data-only network,where data transmit points can be activated on demand, and acontrol-only network where control transmit points are always on. TheBCG2 architecture is explained in greater detail by WirelessCommunications and Networking Conference Workshops (WCNCW) publicationentitled “Energy saving: Scaling network energy efficiency faster thantraffic growth,” (2013 IEEE WCNCW, vol. 12, no. 17, pp. 7-10 Apr. 2013),which is incorporated by reference herein as if reproduced in itsentirety.

FIG. 8 illustrates a phantom cell network architecture for amacro-assisted small cell in which the C-plane and U-plane are splitbetween the macro and small cell in different frequency bands. Thephantom cell network architecture is explained in greater detail bypaper entitled “RAN Evolution Beyond Release 12,” (LTE World Summit,2013), which is incorporated by reference herein as if reproduced in itsentirety.

Aspects of this disclosure provide different sleep/wake-up mechanismsfor downlink and uplink. FIGS. 9A-9C illustrate network configurationsfor different downlink and uplink wake-up procedures. In someembodiments, the uplink wake up procedure may be periodic to maintainuplink based measurements, such as UE/TP association map. Embodimentsmay use uplink sounding reference signals (SRS) or uplink signalingcarried in the physical uplink control channel (PUCCH) to detect activeUEs. The uplink SRS and/or uplink signals may be transmitted by a targetUE, or by a helping UE in D2D communication with the target UE.Detection of active UEs may also be performed by monitoring a physicalrandom access control channel (PRACH). Upon detecting active UEs, thetransmit point may be woken up. Measured uplink signals may originatefrom the selected helping UE(s) of the target UE where UE cooperation isenabled. Wake-up period can be configured by the network. In someembodiments, wake-up procedures can be event-triggered based on a UEfeeding back a change in downlink background interference power.

Embodiments may use on-demand event-triggered based wake-up in thedownlink. The triggering event may be based on the optimization resultof the joint data and control traffic offloading. Embodiments mayprovide periodic wake up in the downlink for periodic traffic such asVoIP. In some embodiments, subsets of a transmit point (TP) group mayperiodically wake-up to send synchronization and broadcast signals inthe downlink direction.

FIG. 6 illustrates an embodiment network architecture for disablingdownlink and uplink operations independently via radio access network(RAN) virtualization. Embodiments may provide support for offloadingboth control and data traffic. Some embodiments may offload UE-specificcontrol channel communications as well. In some embodiments, downlinkgrant and other downlink centric control signaling is turned on/off with(or independently from) the data. In some embodiments, downlink anduplink operations are muted independently from one another. In someembodiments, uplink transmit point sets include different transmitpoints than transmit point sets for DL:

To enable independent muting, uplink grant (and also uplink ACK/NACKPHICH) may be provisioned. The uplink grant provisioning may affect thefinal decision on downlink muting.

Embodiments may use offloading criteria to ensure that the UE observesan active transmit point for receiving downlink control signals.Different traffic offloading strategies may be employed for uplink anddownlink. Offloading strategies may consider data load and control load,possibly on different time scales. Offloading criteria may consider bothdata and control signals when determining load. Activated transmitpoints can transmit any ratio of data to control traffic. Controlchannel offloading may be less dynamic than data channel offloading insome embodiments. In embodiments, uplink communications may begrant-less in nature, e.g., single carrier multiple access, grant-lessmultiple access, etc. When uplink communications are grant-less,downlink muting and uplink grant decisions may be performed jointly. Forexample, an uplink grant may be sent prior to uplink transmission (e.g.,between three and four TTIs depending on various parameters) for thegrant to be received/processed prior to uplink transmission. Embodimentsmay use offloading criteria to ensure that the UE observes an awaketransmit point for receiving uplink grants. Along with other downlinkcontrol information, a UE may receive uplink grants from a transmitpoint that is different than the transmit point transmitting the UE'sdata channel. In embodiments, a controller may be configured to maximizea combined downlink utility function. The following is an example of adownlink utility function:U=Σ_(k,n)U_(k,n)+Σ_(k,n)C_(k,n)+cΣ_(i)f(u_(i), σ_(i))P_(i), whereΣ_(i)f(u_(i), σ_(i))P_(i) is the muting incentive (or activationpenalty), u_(i) is the data loading ratio, σ₁ is the control loadingratio, c is the energy saving coefficient, P_(i) is the normalizedtransmit point power savings, U_(k,n) is the data utility of UE_(k) onresource_(n), and C_(k,n) is the control utility of UE_(k) onresource_(n). FIG. 7 illustrates a graph of consumed power versus outputpower of a transmit point operating in a sleep mode, an active mode, anda max power mode.

In an embodiment, a network controller operates on a group of transmitpoints, which may be a cluster or a candidate set specified by thenetwork layer. A Joint Wideband Muting and Dynamic Point Selectionalgorithm may be employed by the network controller to analyze the dataportion of traffic. BSs with no scheduled UEs will be transitioned to a‘sleep mode,’ and their power consumption may be reduced. Inembodiments, the algorithm could maximize the following utilityfunction: U=Σ_(k,n)U_(k,n)+cΣ_(i∈Muted)(1−u_(i)) P_(i), where u_(i) isthe data loading ratio, c is the energy saving coefficient, and P_(i) isthe normalized transmit point power savings. FIG. 8 illustrates a graphdepicting a system capacity analysis for target constant bit rate of onemegabyte per second (Mbps).

Embodiment techniques for power reduction may be versatile. For example,the techniques may be capable of dynamically adapting to offered trafficloads, of offloading both data and control traffic, of controllingdownlink and uplink operations independently, and of increasing usersatisfaction by exploiting the tradeoffs between spectral efficiency,bandwidth, and latency.

FIG. 9 illustrates a diagram of a power consumption model discussed inIEEE Wireless Communications article entitled “How much energy is neededto run a wireless network? “, IEEE Wireless Communications,” which isincorporated by reference herein as if reproduced in its entirety. FIG.10 illustrates a diagram, a graph, and a chart of a load dependent powerconsumption model for base stations. In this model, the radio frequencyoutput powers of the macro and pico base stations are forty watts andone watt, respectively.

FIG. 11 illustrates a diagram of a power consumption model discussed inIEEE Wireless Communications article entitled “How much energy is neededto run a wireless network? “, IEEE Wireless Communications,” which isincorporated by reference herein as if reproduced in its entirety. FIG.12 illustrates graphs depicting a system capacity analysis for targetconstant bit rate of one megabyte per second (Mbps) for state of the artbase stations.

FIG. 13 illustrates graphs of the power consumption model depicted inFIG. 12. FIGS. 14A-14C illustrate throughput simulations for embodimenttechniques of this disclosure. The simulations were created using thefollowing Common Simulation Parameters: CRAN cluster size: 1, 3, 9, and21 cells; SU MIMO 2×2; Transmit diversity; Maximum transmit base stationtransmit power of forty watts; Linear model for electrical powerconsumption using Matlab post-processor (For all schemes, any BS with noscheduled UE, will be considered in a ‘sleep mode’ and its powerconsumption will be reduced); B=10 MHz; 10 RBGs; 5 RBs/RBG; Perfect CQI;OLLA wideband fixed. The simulations were created in accordance with thefollowing scenarios: 630 UEs under regular loading; 236 UEs under lightloading (⅕ of regular population); UE dropping (based on geometry) bothuniform and non-uniform with randomized pattern (In each 3-cell site,one cell is randomly chosen to be the one with the highest density): UEReceiver configured for MMSE; Traffic model was Full buffer with CBRemulation; Simulated Schemes include single cell SU-MIMO; DPS SU-MIMO;Joint Wideband Muting and DPS SU-MIMO; Energy Saving Coefficient of zero(PF-only utility) and {0.1, 0.3, 0.5, 0.7, 0.9, 1, 1.5, 2, 2.5, 3, 4, 5,10} (Energy-aware muting incentive/turning-on penalty). FIG. 15illustrates a chart of simulation scenario results.

FIG. 16 illustrates a block diagram of a processing system that may beused for implementing the devices and methods disclosed herein. Specificdevices may utilize all of the components shown, or only a subset of thecomponents, and levels of integration may vary from device to device.Furthermore, a device may contain multiple instances of a component,such as multiple processing units, processors, memories, transmitters,receivers, etc. The processing system may comprise a processing unitequipped with one or more input/output devices, such as a speaker,microphone, mouse, touchscreen, keypad, keyboard, printer, display, andthe like. The processing unit may include a central processing unit(CPU), memory, a mass storage device, a video adapter, and an I/Ointerface connected to a bus.

The bus may be one or more of any type of several bus architecturesincluding a memory bus or memory controller, a peripheral bus, videobus, or the like. The CPU may comprise any type of electronic dataprocessor. The memory may comprise any type of system memory such asstatic random access memory (SRAM), dynamic random access memory (DRAM),synchronous DRAM (SDRAM), read-only memory (ROM), a combination thereof,or the like. In an embodiment, the memory may include ROM for use atboot-up, and DRAM for program and data storage for use while executingprograms.

The mass storage device may comprise any type of storage deviceconfigured to store data, programs, and other information and to makethe data, programs, and other information accessible via the bus. Themass storage device may comprise, for example, one or more of a solidstate drive, hard disk drive, a magnetic disk drive, an optical diskdrive, or the like.

The video adapter and the I/O interface provide interfaces to coupleexternal input and output devices to the processing unit. Asillustrated, examples of input and output devices include the displaycoupled to the video adapter and the mouse/keyboard/printer coupled tothe I/O interface. Other devices may be coupled to the processing unit,and additional or fewer interface cards may be utilized. For example, aserial interface such as Universal Serial Bus (USB) (not shown) may beused to provide an interface for a printer.

The processing unit also includes one or more network interfaces, whichmay comprise wired links, such as an Ethernet cable or the like, and/orwireless links to access nodes or different networks. The networkinterface allows the processing unit to communicate with remote unitsvia the networks. For example, the network interface may providewireless communication via one or more transmitters/transmit antennasand one or more receivers/receive antennas. In an embodiment, theprocessing unit is coupled to a local-area network or a wide-areanetwork for data processing and communications with remote devices, suchas other processing units, the Internet, remote storage facilities, orthe like.

FIG. 17 illustrates a block diagram of an embodiment of a communicationsdevice 1700, which may be equivalent to one or more devices (e.g., UEs,NBs, etc.) discussed above. The communications device 1700 may include aprocessor 1704, a memory 1706, a plurality of interfaces 1710, 1712,1714, which may (or may not) be arranged as shown in FIG. 17. Theprocessor 1704 may be any component capable of performing computationsand/or other processing related tasks, and the memory 1706 may be anycomponent capable of storing programming and/or instructions for theprocessor 1704. The interfaces 1710, 1712, 1714 may be any component orcollection of components that allows the communications device 1700 tocommunicate with other devices.

In an embodiment, a method for a helping user equipment (UE) in awireless communications network is provided. In this embodiment, themethod includes transmitting an uplink signal to a first physicaltransmit point (TP), where the uplink signal is associated with a targetUE that is engaged in device-to-device (D2D) communications with thehelping UE, and the uplink signal is associated with a downlinkre-activation criteria for waking the first physical TP. In one example,the downlink re-activation criteria comprises at least one of aninterference level experienced by the target UE, a request to providewireless access, and a quality of a discovery signal of the uplinksignal. In the same example, or another example, the method furtherincludes deactivating a downlink transmitter of the first physical TPwithout deactivating an uplink receiver of the first physical TP, andreactivating the downlink transmitter of the first physical TP when theuplink signal satisfies the downlink re-activation criteria. In such anexample, the method may further include determining that a downlinktransmission for the target UE has been offloaded from a second physicalTP to the first physical TP, wherein the first physical TP and thesecond physical TP are associated with a same virtual TP, and performingthe downlink transmission to the target UE using the downlinktransmitter. In such an example, the second physical TP may communicateone or both of data traffic and control signaling with the target UEduring a first period, and the first physical TP may communicate the atleast one of the data traffic or the control signaling with the targetUE during a second period after offloading at least one of the datatraffic and the control signaling from the second physical TP to thefirst physical TP. Additionally, in such an example, the offloading mayinclude offloading at least one of the data traffic and the controlsignaling from the second physical TP to the first physical TP for atime period in the order of a Transmission Time Interval (TTI).Additionally or alternatively, in such an example, the at least one ofthe data traffic or the control signaling may be offloaded withoutcausing the target UE to undertake a handover. Additionally oralternatively, in such an example, offloading the at least one of thedata traffic and the control signaling from the second physical TP tothe first physical TP may include offloading downlink control signalingfrom the second physical TP to the first physical TP, and/or the methodmay further include downlink muting the second physical TP afteroffloading the downlink control signaling to the first physical TP. Thesecond physical TP may comprise a macro base station and the firstphysical TP comprises a low power node, and the method may furtherinclude downlink muting the macro base station after offloading thedownlink control signaling from the macro base station to the low powernode. In any one of the preceding examples, or in another example,offloading at least one of the data traffic and the control signalingfrom the second physical TP to the first physical TP may includeoffloading downlink data traffic from the second physical TP to thefirst physical TP. In any one of the preceding examples, or in anotherexample, offloading at least one of the data traffic and the controlsignaling from the second physical TP to the first physical TP includesoffloading uplink data traffic from the second physical TP to the firstphysical TP. In any one of the preceding examples, or in anotherexample, offloading at least one of the data traffic and the controlsignaling from the second physical TP to the first physical TP includesoffloading uplink control signaling from the second physical TP to thefirst physical TP.

In any one of the preceding examples, or in another example, theoffloaded control signaling may include UE-specific control traffic. Inany one of the preceding examples, or in another example, the uplinksignal satisfies the downlink re-activation criteria when the uplinksignal indicates that the interference level experienced by the targetUE exceeds a threshold. In such an example, the interference levelexperienced by the target UE may include a background interference levelexperienced by the target UE. In any one of the preceding examples, orin another example, the uplink signal satisfies the downlinkre-activation criteria when the quality of the discovery signal exceedsa threshold. In such an example, the discovery signal may be an uplinksounding signal and the quality may be a received signal power of theuplink sounding signal. In any one of the preceding examples, or inanother example, the method further includes periodically transmittingthe uplink signal to the first TP. In accordance with anotherembodiment, a helping user equipment (UE) is provided. The helping UEincludes a receiver, a transmitter, and a processor operatively coupledto the receiver and the transmitter. The processor is configured totransmit an uplink signal to a first physical transmit point (TP), wherethe uplink signal is associated with a target UE that is engaged indevice-to-device (D2D) communications with the helping UE and the uplinksignal is associated with a downlink re-activation criteria for wakingthe first physical TP. In one example, the downlink re-activationcriteria comprises at least on of an interference level experienced bythe target UE, a request to provide wireless access, and a quality of adiscovery signal of the uplink signal. In the same example, or anotherexample, the uplink signal satisfies the downlink re-activation criteriawhen the uplink signal indicates that the interference level experiencedby the target UE exceeds a threshold. In any one of the precedingexamples, or another example, the interference level experienced by thetarget UE comprises a background interference level experienced by thetarget UE. In any one of the preceding examples, or another example, theuplink signal satisfies the downlink re-activation criteria when thequality of the discovery signal exceeds a threshold. In any one of thepreceding examples, or another example, the discovery signal is anuplink sounding signal and the quality is a received signal power of theuplink sounding signal. In any one of the preceding examples, or anotherexample, the processor is further configured to periodically transmitthe uplink signal to the first TP.

Although the description has been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade without departing from the spirit and scope of this disclosure asdefined by the appended claims. Moreover, the scope of the disclosure isnot intended to be limited to the particular embodiments describedherein, as one of ordinary skill in the art will readily appreciate fromthis disclosure that processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped, may perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein. Accordingly, the appended claims are intended to include withintheir scope such processes, machines, manufacture, compositions ofmatter, means, methods, or steps.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

What is claimed is:
 1. A method, the method comprising: receiving, by anuplink receiver of a transmit point (TP), an uplink signal comprisinginformation associated with a target user equipment (UE), wherein adownlink transmitter of the TP is deactivated when the uplink signal isreceived; activating, by the TP, the downlink transmitter of the TPbased on the information associated with the target UE; andtransmitting, by the downlink transmitter of the TP, a downlink signalto the target UE.
 2. The method of claim 1, the receiving comprises:receiving the uplink signal from one of the target UE, a helping UE, arelay station, a controller, or a second TP different from the TP. 3.The method of claim 1, wherein the information associated with thetarget UE comprises a wakeup indication.
 4. The method of claim 1,wherein the information associated with the target UE indicates aninterference level experienced by the target UE, and the activatingcomprises: activating, by the TP, the downlink transmitter of the TPbased on the interference level exceeding an interference levelthreshold.
 5. The method of claim 4, wherein the interference levelexperienced by the target UE comprises a background interference levelexperienced by the target UE.
 6. The method of claim 1, wherein theuplink signal comprises a discovery signal, and the activatingcomprises: activating, by the TP, the downlink transmitter of the TPbased on a quality of the discovery signal exceeding a qualitythreshold.
 7. The method of claim 6, wherein the quality of thediscovery signal comprises a received signal power of the discoverysignal.
 8. The method of claim 1, wherein the uplink signal comprises arequest for service.
 9. A transmit point (TP), the TP comprising: aprocessor; an uplink receiver coupled to the processor; and a downlinktransmitter coupled to the processor, the uplink receiver configured toreceive an uplink signal comprising information associated with a targetuser equipment (UE), wherein the downlink transmitter is deactivatedwhen the uplink signal is received, the processor configured to activatethe downlink transmitter of the TP based on the information associatedwith the target UE, and the downlink transmitter configured to transmita downlink signal to the target UE.
 10. The TP of claim 9, the uplinkreceiver configured to receive the uplink signal by: receiving theuplink signal from one of the target UE, a helping UE, a relay station,a controller, or a second TP different from the TP.
 11. The TP of claim9, wherein the information associated with the target UE comprises awakeup indication.
 12. The TP of claim 9, wherein the informationassociated with the target UE indicates an interference levelexperienced by the target UE, and the processor is configured toactivate the downlink transmitter by: activating the downlinktransmitter of the TP based on the interference level exceeding aninterference level threshold.
 13. The TP of claim 12, wherein theinterference level experienced by the target UE comprises a backgroundinterference level experienced by the target UE.
 14. The TP of claim 9,wherein the uplink signal comprises a discovery signal, and theprocessor is configured to activate the downlink transmitter by:activating the downlink transmitter of the TP based on a quality of thediscovery signal exceeding a quality threshold.
 15. The TP of claim 14,wherein the quality of the discovery signal comprises a received signalpower of the discovery signal.
 16. The TP of claim 9, wherein the uplinksignal comprises a request for service.
 17. A non-transitorycomputer-readable device having instructions stored thereon that, whenexecuted by a machine transmit point (TP), cause the TP to performoperations, the operations comprising: receiving, by an uplink receiverof the TP, an uplink signal comprising information associated with atarget user equipment (UE), wherein a downlink transmitter of the TP isdeactivated when the uplink signal is received; activating, by the TP,the downlink transmitter of the TP based on the information associatedwith the target UE; and transmitting, by the downlink transmitter of theTP, a downlink signal to the target UE.
 18. The non-transitorycomputer-readable device of claim 17, the receiving comprises: receivingthe uplink signal from one of the target UE, a helping UE, a relaystation, a controller, or a second TP different from the TP.
 19. Thenon-transitory computer-readable device of claim 17, wherein theinformation associated with the target UE comprises a wakeup indication.20. The non-transitory computer-readable device of claim 17, wherein theinformation associated with the target UE indicates an interferencelevel experienced by the target UE, and the activating comprises:activating, by the TP, the downlink transmitter of the TP based on theinterference level exceeding an interference level threshold.